全文获取类型
收费全文 | 1596篇 |
免费 | 40篇 |
国内免费 | 23篇 |
专业分类
测绘学 | 53篇 |
大气科学 | 159篇 |
地球物理 | 279篇 |
地质学 | 616篇 |
海洋学 | 124篇 |
天文学 | 289篇 |
综合类 | 11篇 |
自然地理 | 128篇 |
出版年
2023年 | 9篇 |
2021年 | 17篇 |
2020年 | 17篇 |
2019年 | 17篇 |
2018年 | 34篇 |
2017年 | 28篇 |
2016年 | 40篇 |
2015年 | 25篇 |
2014年 | 44篇 |
2013年 | 71篇 |
2012年 | 54篇 |
2011年 | 74篇 |
2010年 | 74篇 |
2009年 | 117篇 |
2008年 | 78篇 |
2007年 | 96篇 |
2006年 | 77篇 |
2005年 | 86篇 |
2004年 | 53篇 |
2003年 | 48篇 |
2002年 | 52篇 |
2001年 | 41篇 |
2000年 | 40篇 |
1999年 | 29篇 |
1998年 | 26篇 |
1997年 | 21篇 |
1996年 | 20篇 |
1995年 | 19篇 |
1994年 | 21篇 |
1993年 | 16篇 |
1992年 | 15篇 |
1991年 | 14篇 |
1990年 | 14篇 |
1988年 | 12篇 |
1986年 | 11篇 |
1985年 | 15篇 |
1984年 | 13篇 |
1983年 | 22篇 |
1982年 | 16篇 |
1981年 | 15篇 |
1980年 | 12篇 |
1979年 | 9篇 |
1978年 | 9篇 |
1977年 | 8篇 |
1976年 | 15篇 |
1975年 | 8篇 |
1973年 | 15篇 |
1972年 | 15篇 |
1971年 | 11篇 |
1970年 | 9篇 |
排序方式: 共有1659条查询结果,搜索用时 17 毫秒
981.
982.
Managing authorities in Scandinavia arrange public information meetings when members of the public express fear because wolves or brown bears approach human settlements. This study aimed to increase the understanding of the potential effect of information meetings on self-reported fear of wolves and brown bears. In total, 198 participants completed questionnaires before and after the information meetings. Nine follow-up interviews were held 1 year later. The quantitative analyses revealed that participants who found the information credible reported a significant increase in social trust and a decrease in vulnerability and fear. The qualitative analyses pointed to the importance of information content and meta-communication, for example, nonverbal cues. It is proposed that, among participants who find the information credible, information meetings may change the appraisal of wolves and brown bears, and therefore they might prove useful as an intervention to address fear of these animals. 相似文献
983.
Susanne Lildal?AmsinckEmail author Erik?Jeppesen Frank?Landkildehus 《Journal of Paleolimnology》2005,33(1):39-51
Subfossil zooplankton assemblages (Cladocera 22 taxa, Rotifera 1 taxon) were identified from the surface sediments of 36 shallow (median depth = 0.7 m) Danish coastal brackish lakes differing in epilimnic salinity (SAL, range 0.2–17.4), summer-mean total phosphorus (TP, 27–327 g l–1) and total nitrogen (TN, 0.850–2.629 mg l–1), as well as in submerged macrophyte coverage and planktivorous fish density (PL-CPUE). Cladoceran species richness declined significantly with increasing SAL, TP and TN, while no significant correlation was found to either PL-CPUE, macrophyte coverage or lake surface area. Bonferroni-adjusted forward selection within canonical correspondence analysis (CCA) showed that 22.1% of the variation in zooplankton data was explained by PL-CPUE, SAL and TP uniquely; each variable explaining an almost equally significant amount of variation in the zooplankton data. Predictive models to infer PL-CPUE, SAL and TP were developed using variance weighted-averaging (WA) procedures. Almost similar values of boot-strapped coefficient of determination (r2boot-strapped 0.22–0.38) were produced by the WA inference models of PL-CPUE, SAL and TP, while the inference models of TP produced the lowest boot-strapped root-mean-squared-error of prediction (RMSEPboot-strapped 0.29–0.36 log(TP + 1), g l–1). Yet, zooplankton TP and SAL optima (WA) were strongly correlated (r2 = 0.46), while PL-CPUE optima (WA) were independent of both TP and SAL optima, indicating that only the PL-CPUE inference models are suitable for making reconstructions. 相似文献
984.
985.
Atmospheric stability conditions over the water surface can affect the evaporative and convective heat fluxes from the water surface. Atmospheric instability occurred 72.5% of the time and resulted in 44.7 and 89.2% increases in the average and maximum estimated evaporation, respectively, when compared to the neutral condition for a small shallow lake (Binaba) in Ghana. The proposed approach is based on the bulk-aerodynamic transfer method and the Monin-Obukhov similarity theory (MOST) using standard meteorological parameters measured over the surrounding land. For water surface temperature, a crucial parameter in heat flux estimation from water surfaces, an applicable method is proposed. This method was used to compute heat fluxes and compare them with observed heat fluxes. The heat flux model was validated using sensible heat fluxes measured with a 3-D sonic anemometer. The results show that an unstable atmospheric condition has a significant effect in enhancing evaporation alongside the sensible heat flux from water surfaces. 相似文献
986.
The solubilities of synthetic, natural and biogenic aragonite and calcite, in natural seawater of 35%. salinity at 25°C and 1 atm pressure, were measured using a closed system technique. Equilibration times ranged up to several months. The apparent solubility constant determined for calcite of 4.39(±0.20) × 10?7 mol2 kg?2 is in good agreement with other recent solubility measurements and is constant after 5 days equilibration. When we measured aragonite solubility we observed that it decreased with increasing time of equilibration. The value of 6.65(±0.12) × 10?7 mol2 kg?2, determined for equilibration times in excess of 2 months, is significantly less than that found in other recent measurements, which employed equilibration times of only a few hours to days. No statistically significant difference was found among the synthetic, natural and biogenic material. Solid to solution ratio, contamination of aragonite with up to 10 wt% calcite and recycling of the aragonite made no statistically significant difference in solubility when long equilibration times were used.Measured apparent solubility constants of aragonite and calcite are respectively 22( ± 3)% and 20( ± 2)% less than apparent solubility constants calculated from thermodynamic equilibrium constants and seawater total activity coefficients. These large differences in measured and calculated apparent solubility constants may be the result of the formation of surface layers of lower solubility than the bulk solid. 相似文献
987.
988.
Frank Gaardsted Meng Zhou Vladimir Pavlov Alexey Morozov Kurt S. Tande 《Deep Sea Research Part I: Oceanographic Research Papers》2010,57(11):1465-1473
Data collected on a cruise in January 2008, using a laser optical plankton counter, conductivity–temperature–depth sensors, and a lowered acoustic Doppler current profiler, was used to study the mesoscale distribution and advection of overwintering Calanus finmarchicus in its deep water winter habitat off the shelf of northern Norway. The overwintering animals were generally located immediately below the Atlantic Water (AW) in Arctic Intermediate Water (AIW), in the 600–1200 m depth range. The depth of the interface between AW and AIW varied considerably in the area and this was clearly reflected in the C. finmarchicus distribution. Maximum abundance varied from about 80 ind m?3 to more than 200 ind m?3 at the different stations. Current measurements showed the richness of mesoscazle eddies, with speeds exceeding 70 cm s?1 at the surface and rapidly decreasing with depth. In the main overwintering layer the eddy features were also clearly seen, but with speeds generally below 20 cm s?1. C. finmarchicus were found in the whole survey area, but they were not homogeneously distributed. Advection of the copepods resulted in relatively high local rates of change in overwintering C. finmarchicus abundance with mean value of 8% per day in the area. It is clear that mesoscale physical processes greatly contribute to the variability in the abundance of overwintering C. finmarchicus off the shelf of northern Norway. The collected data are also a valuable addition to the generally sparse datasets on the C. finmarchicus winter distribution and the role of the Lofoten basin in the large scale system is also discussed. 相似文献
989.
990.